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Cool & Warm Season Turfgrasses and Their Care

The change in seasons from summer to fall presents an optimal time for the renovation and establishment of cool-season turf grasses and a period of preparation for warm-season grasses before their winter dormancy. Take advantage of the relatively mild weather of the months of September and October to get your turf ready for winter and next year's growing season. The following summation is taken from the Virginia Cooperative Extension, Publication Number 430-520, Dec. 2004. For detailed information and instructions, please download the complete article provided in the attached .pdf file.

STRATEGIES FOR COOL-SEASON TURF GRASSES

Late-summer to mid-fall is the best time to establish cool-season turf grass such as tall fescue, Kentucky bluegrass, fine-leaf fescues, and perennial ryegrass. Sod establishment is also favored at this time of year. If you have to re-establish turf grass, it's important to pinpoint any problems your grass has to avoid future problems.

Soil testing

The first step towards correcting an existing problem lawn or establishing new turf is to test your soil. This very cost-effective diagnosis of your soil's fertility and pH status is quite often the answer to the question of "Why did my turf fail?" Many of Virginia's soils are very acid and probably require a supplemental lime application.

Select the best turf grass

What cool-season grass to choose? Your local lawn and garden center, farmer's cooperative or a turf and landscape supply store can help you determine the best varieties for your area.

Soil preparation prior to establishment

For new plantings, tilling the soil to a 4- to 6-inch depth is desirable prior to seeding. This gives you an opportunity to put the information from a soil test to work and incorporate any recommended lime or starter fertilizer that will aid turf establishment. Aerating or dethatching can help prep the soil prior to planting. Simply applying seed over the top of an existing turf usually does nothing more than feed birds and wildlife.

Initial irrigation and mowing strategies

After planting, irrigate lightly and frequently, avoiding too much water that could wash away or drown the seed. As establishment progresses, gradually cut back on the amount of water you apply in order to start promoting a deep root system. For sod establishment, larger amounts of water can be applied less frequently because sod provides soil and root mass that hold moisture.

When mowing established turf, never remove more than one-third of the leaf blade.

Weed control options after establishment

Weed control recommendations are split into late summer/fall and spring/early summer. By promoting a rapid establishment of seeded turf grass (proper seeding rates & irrigation), you can avoid most weed pitfalls. Seedlings are much more sensitive to chemical applications than mature plants. Consult the Virginia Cooperative Extension Pest Management Guides, publications 456-016, 456-017, and 456-018 at http://www.ext.vt.edu/pubs/pmg/, for help in selecting the best weed control options available.

Fertility

You can make supplemental nitrogen applications later in the fall after establishment if you want a boost in growth or color. During September, October and November, applications of 1/2 to 1 pound of water-soluble nitrogen per 1000 square feet on 4- to 6-week intervals are very beneficial. It is possible in many locations that a single fall application will suffice to meet the turf's needs.

Cultivation

Core aeration and vertical mowing are two methods of turf cultivation that can provide long-term benefits if done properly and at the right time of year. Each of these activities is important, but also disruptive to the soil surface and the turf. It's best to refrain from aerifying or dethatching cool-season turf grasses until the fall when turf recovery can be optimized by fertilization and irrigation or rainfall.

Pest control

There are several pre-emergent herbicides that, when applied in August or September, depending on location, will control annual bluegrass, as well as many other winter annual weeds (henbit, chickweed, geranium, etc.). However, remember that these materials will also prevent cool-season turf grass seed germination if you are planning a fall planting. There also are numerous postemergence broadleaf herbicides available for fall weed control.

Diseases and insects are typically of limited importance during the fall, and fall nitrogen fertilizer programs can suppress their occurrence. For new seedlings, it is wise to use fungicide-treated seed to combat seedling damping-off.
There is potential for early-fall applications of certain insecticides for grub control, but the ideal period for their control is between July and August. A complete listing of recommended pesticides and the pests they target is provided in the Virginia Cooperative Extension Pest Management Guides at http://www.ext.vt.edu/pubs/pmg/.

STRATEGIES FOR WARM-SEASON TURF GRASSES

Fertility

Warm-season turf grasses (Bermuda grass and zoysiagrass across much of the commonwealth, in addition to St. Augustine grass and centipede grass in the Tidewater) will go dormant after the first killing frost. However, there is time to benefit from nitrogen fertility in the early fall.

Pest control

There are more preemergence weed-control options for dormant, non-overseeded warm-season turf grasses than for cool-season turf because warm-season grasses should not be planted now (unless one is installing sod in early to mid-fall). The dormant warm-season grass provides little to no competition to cool-season weeds, thus weed control is often necessary. Check the Pest Management Guides to stay abreast of the most recent releases in superior herbicides. Insect and disease pressure for a grass preparing for dormancy are minimal.

Cultivation

Fall is too late in the growing season to safely aerify or vertical mow warm-season turf grasses. Do this in late spring or early summer.

Overseeding

A unique aspect of warm-season turf grass management is the often used practice of the overseeding of ryegrass (Lolium spp.) to provide winter color and an actively growing playing surface for sporting venues. Perennial ryegrass and annual ryegrass are the major cool-season grasses used for this form of "overseeding." However, as cool-season grass will compete for nutrients, water, and light with warm-season grass, the overseeded grass will eventually die, which will result in a very poor quality warm-season turf for a period of weeks. Overseeding also alters strategies for winter weed control because most preemergence herbicides will also control the overseeded grass. Timing of the applications and/or choice of the appropriate material are critical for success.

While annual ryegrass is significantly cheaper per pound of seed and will germinate and establish quicker than any other turf grass, perennial ryegrass is preferable for the highest quality turf.


For the complete article and more detailed tips on maintaining your lawn, please download the .pdf file attached.

Authors: Michael Goatley, Jr., Extension Turf grass Specialist; and Shawn Askew, Extension Turf grass Weed Specialist; Virginia Tech. Publication Number 430-520, Posted Dec. 2004. Virginia Cooperative Extension, www.ext.vt.edu.